DR. W. M. HICKS : A CRITICAL STUDY OF SPECTRAL SERIES. 405 



d\ = -02, whilst 38203 corresponds to 30f<5 with dX = '01. They should form 

 portions of doublets with lines at 39977'48, 39995'58. None have been observed, but 

 it must be remembered that these are close to the end of the observed region where only 

 the stronger lines would be seen. Sounding with (e+u) we find lines (l) 28530*91, 

 (3) 28548'26 respectively, e+u '71 and e + w + "04 behind the expected D.^ lines 

 showing no lines at v. 2 ahead, which should be visible if they existed. We may, 

 therefore, conclude the two lines in question belong to a doublet set. With regard to 

 the suspected D 13 line (38111) we find in this neighbourhood 



(1)38134-61 1780-23 [39915-84] 815'20 (in) 40731'04 



(1) 38129-37 1778-21 (l) 39907'58 810'36 (l) 40717'94 



(In) 38108'GO 



Calculation shows that the first lines of these sets give with D n (2) separations 

 depending on displacements 43^ (d\ = 0), ^S(d\= - 0l), 48^ (d\ = - - 03). All 

 that can be said is that these lines may be the required satellite sets. As, however, 

 a displacement of ^ only produces a change of about '05 in X it is not possible to get 

 any certainty. It is further possible that some of the set may belong to parallel 

 series. For instance 38108 = (2^) 38129. The first two are, however, so close 

 d\ '00 and '01 that they are entered as D ]3 lines. 



For the second group 20305 is a 14<5 displacement from 20581. We should expect 

 the corresponding m = 2 line about the same displacement from 38366. This is 

 satisfied by the line (l) 38292'32 giving 14(5 with d\ = '01. There is also a doublet 

 (l) 38285'86, 1778'08, (l) 40063'94 with normal separation and displaced 15^ with 

 d\ = '00. The first D (l) is displaced 122^ from its D u line 20305 and the second 

 by an extra 73^. If the D n (2) line is taken as 38285 the calculated line with 

 122^(5 is 37611 '59. There is no line here, but there is a doublet, which with this line 

 may be written 



(2) 37606'15 1780-831 



> (1) 39386-98 

 [37611'59] 1775-39J 



The mean of these two separations is 1778'! 1 or the normal /,. We have here a 

 parallel inequality due to 2^ displacement in 39386 and an extra 2<^ in 37606, or 

 37606 is 123|-(5 ahead of D n . 



Again calculating the 73%S displacement on 30706 the line should be 37174"40. It 

 is not observed but there is a triplet close to it showing a similar inequality to the 

 former. It is 



(1)37159-39 1774-38] 



> (1)38940-81 813-67 (<l)39754'48 

 (In) 37166-43 1781'42J 



